Carphone Warehouse-owned TalkTalk, which has more than 4 million ISP customers and owns the Tiscali and AOL brands, claimed the government's plan was based on filesharers being "guilty until proven innocent" and constituted an infringement of human rights.

"The approach is based on the principle of 'guilty until proven innocent' and substitutes proper judicial process for a kangaroo court," said Andrew Heaney, the executive director of strategy and regulation at TalkTalk. "We know this approach will lead to wrongful accusations."

The government plans to look at increased action against illegal downloaders, including potentially suspending the accounts of persistent offenders, from July 2011 if a 70% reduction in online piracy is not achieved by sending warning letters. Customers will have the right to appeal if they are targeted and their connection subjected to technical measures.

"If the government moves to stage two, we would consider that extra-judicial technical measures, and would look to appeal the decision [to the courts] because it infringes human rights," Heaney said. "TalkTalk will continue to resist any attempts to make it impose technical measures on its customers unless directed to do so by a court or recognised tribunal."

BT, the largest ISP in the UK, said it "remains concerned" about some of the government's proposals and is "interested to hear whether or not customers will have some form of fair legal hearing before their broadband supplier is required to take any action against them".

Chris Watson, the head of telecoms law at legal firm CMS Cameron McKenna, said that the opportunity to appeal was "very different to the legal safeguards that normally apply to the determination of the infringement of intellectual property rights and it may be incompatible with the European convention on human rights".

However, Tony Ballard, partner at media and entertainment law firm Harbottle & Lewis, said that Mandelson's plan to suspend internet connections did not breach human rights regulations.

"This issue over whether removing someone's internet access breaches some fundamental right has been quite clearly settled by the European court of justice," Ballard added. "It ruled in a Spanish filesharing case last year that a user's fundamental rights are not absolute but have to be weighed against the rights of others, including copyright owners."

Ballard said that it is for the "individual states and their courts to hold the balance". He added that Mandelson clearly had an eye on France where a tough "three strikes" cut-off policy has been implemented and approved by the French legislature.

"The key questions are going to be around how the ISPs will manage the burden of proof, who is going to be responsible for the final decision to deny someone access to the internet and how that denial can be challenged in court," he added.

• To contact the MediaGuardian news desk email editor@mediaguardian.co.uk or phone 020 3353 3857. For all other inquiries please call the main Guardian switchboard on 020 3353 2000.

• If you are writing a comment for publication, please mark clearly "for publication".